As the demand for electrical power increases over the past decades, more and more hydroelectric power plants have been built to convert hydropower into electricity. The hydroelectric power plants, however, cause serious damages to the natural ecosystem. For example, dams often block the natural migration paths of fish. In addition, building dams and reservoirs involve large scale of displacing people, particularly in third-world countries where population is dense. Moreover, when dams become aged and start to degrade, they become a threat to people living downstream. Thus, there is a need to develop new technologies that are more environmental friendly to utilize the hydropower.